Active matrix substrate, and x-ray imaging panel

1. An active matrix substrate comprising: a gate line; a data line that intersects with the gate line; a photoelectric conversion element that is provided in a pixel defined by the gate line and the data line; a bias line that is connected with the photoelectric conversion element; a bias terminal that is connected with the bias line and supplies a bias voltage to the bias line; a first line to which a predetermined voltage higher than the bias voltage is supplied; and a first protection circuit that is connected in a reverse-biased state between the bias terminal and the first line, and is formed with a nonlinear element.

2. The active matrix substrate according to claim 1 , further comprising: a switching element that is connected to the gate line, the data line, and the photoelectric conversion element; a gate terminal that is connected with the gate line; and a pair of second protection circuits that are formed with nonlinear elements and are provided with respect to the gate terminal, wherein the gate line is one of a plurality of gate lines, wherein the pair of second protection circuits are connected between the gate terminal, commonly, and different ones of a plurality of other gate lines, respectively, and each of the pair of second protection circuits is in a forward-biased state when the gate line connected with the gate terminal is in a selected state, and is in a reverse-biased state when the said other gate line connected to the second protection circuit is in a selected state.

3. The active matrix substrate according to claim 2 , further comprising: a data terminal connected with the data line; and a third protection circuit that is formed with a nonlinear element, and is connected with the data terminal, wherein the data terminal has a potential higher than a predetermined potential of the first line, and the third protection circuit is connected in a reverse-biased state between the data terminal and the first line.

4. The active matrix substrate according to claim 3 , wherein the photoelectric conversion element is formed with a photodiode, and each of the first protection circuit, the second protection circuit, and the third protection circuit includes a photodiode that has the same structure as that of the photoelectric conversion element, and a light-shielding layer that covers the photodiode.

5. The active matrix substrate according to claim 4 , wherein each of the first protection circuit, the second protection circuit, and the third protection circuit further includes a switching element for protection circuit, the switching element being connected in series with the photodiode of each of the first protection circuit, the second protection circuit, and the third protection circuit.

6. The active matrix substrate according to claim 2 , further comprising: a data terminal connected with the data line; a second line to which a voltage higher than a voltage supplied to the data terminal is supplied; and a third protection circuit that is formed with a nonlinear element, and is connected in a reverse-biased state between the data terminal and the second line.

7. The active matrix substrate according to claim 2 , further comprising: an insulating film between the photoelectric conversion element and the switching element, wherein the photoelectric conversion element is arranged so as to overlap with the switching element when viewed in a plan view, with the insulating film being interposed therebetween.

8. An X-ray imaging panel comprising: the active matrix substrate according to claim 1 ; and a scintillator that is provided on a surface on one side of the active matrix substrate, and converts irradiated X-rays into fluorescence.

9. The X-ray imaging panel according to claim 8 , further comprising: a driving circuit that is connected with the active matrix substrate and scans the gate lines; and a readout circuit that is connected with the active matrix substrate and reads out charges corresponding to fluorescence converted by the scintillator through the data lines.